Substituted sulfoxide compounds or their enantiomers (viz., Omeprazole, Lansoprazole, Pantoprazole, Rabeprazole and Ilaprazole) are known inhibitors of gastric acid secretion and are used as anti-ulcer agents. The sulfur atom of the sulfoxide group in asymmetrically substituted sulfoxide is chiral. This type of chiral sulfoxides has been discussed in the scientific literature since the late seventies, even though there is no literature evidence for efficient asymmetric process for the synthesis of the single enantiomers thereof.
The single enantiomers of pharmacologically active compounds have met an increased interest in the last years because of improved pharmacokinetic and biological properties. Therefore, there is a demand for an enantioselective process that can be used in large scale manufacture of the single enantiomers of pharmacologically active compounds, such as for instance optically pure, substituted 2-(2-pyridinylmethylsulphinyl)-1H-benzimidazoles.
The resolution processes of racemates of substituted sulfoxides are disclosed in DE 4035455. According to the disclosed process racemic sulfoxide is converted to a diastereomeric mixture, followed by separation of diastereomers and isolation of desired isomer from the separated diastereomer.
The international patent application WO96/02535 describes a process for the enantioselective synthesis of proton pump inhibitors using chiral titanium complexes. The resolution processes disclosed in the above prior arts are lengthy and tedious. They involve multiple steps during synthesis and purification to obtain the desired products.
Hence, there is a need for an improved and effective enantioselective process for large scale production of substituted sulfoxide compounds.